Statfjord Field is one of the largest and oldest fields on NCS and operates with platforms Stafjord A, B and C. In recent years, slot recovery to drill more wells has posed a big challenge to deliver wells with Gas Lift design due to extensive and time & cost consuming P&A and casing cut & pull operations. As Statfjord is operating in late life phase using artificial gas lift as a secondary recovery approach, well designs to meet NORSOK well integrity casing design requirements is a key design focus. Along with the above mentioned technical challenges, improving operational excellence has driven the concept of innovative casing design with 11 ¾″ liners. This design eliminates the time spent on extensive casing retrieval operations. In addition, reduces time and risks associated with drilling 17 ½″ section that requires changing from 13 5/8″ to 21 ¼″ BOP, higher flow rates for hole cleaning and larger volume of cutting injection, and waiting 13 3/8″ casing hangers that are crucial long lead item. Installation of 11 ¾″ liner and cementing 9 5/8″ casing in tight ECD margins were identified as high priority design goals in the early planning phase. To address aforementioned challenges and meet design goal in time and cost efficient way, innovative ideas were a fundamental necessity.

This paper discusses the background behind need for a new gas lift well design for well 33/12-B-42 B, casing design approach, challenges faced during planning and learnings from operations. Key operational highlights leading to successful well delivery were: optimization of 11 ¾″ liner depth to meet gas lift formation strength requirements; successful 11 ¾″ liner cement job with rotation to secure the secondary barrier envelop; and opening the narrow ECD window between 9 5/8″ casing and 11 ¾″ liner with to Low Rheology Oil Based Mud (LROBM) after drilling 10 5/8″ × 12 ¼″ section with Conventional Oil Based Mud (COBM). Successful cement job on 9 5/8″ casing facilitated the improved production profile by placement of production packer in 9 5/8″ casing instead of 7″ liner. The new gas lift well design has opened ~ 40 slots for 13 3/8″ exit on Statfjord and it is expected to reduce the time consuming casing retrieval and slot recovery operations

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